Measurement of the Nucleon $F^n_2/F^p_2$ Structure Function Ratio by the Jefferson Lab MARATHON Tritium/Helium-3 Deep Inelastic Scattering Experiment

Understand

The ratio of the nucleon $F_2$ structure functions, $F_2^n/F_2^p$, is determined by the MARATHON experiment from measurements of deep inelastic scattering of electrons from $^3$H and $^3$He nuclei.

• The experiment was performed in the Hall A Facility of Jefferson Lab and used two high resolution spectrometers for electron detection, and a cryogenic target system which included a low-activity tritium cell.
• The data analysis used a novel technique exploiting the mirror symmetry of the two nuclei, which essentially eliminates many theoretical uncertainties in the extraction of the ratio.
• The results, which cover the Bjorken scaling variable range $0.19 < x < 0.83$, represent a significant improvement compared to previous SLAC and Jefferson Lab measurements for the ratio.